An afterloading device as such (also known as “afterloader”) is known, and currently marketed by the applicant. In the known afterloading device, usually, an Iridium-192 or Cobalt-60 radioactive source is used for effectuating brachytherapy. The radioactive source is stored in a radiation shielding vault inside a housing of the afterloading device. Particularly, the afterloading device may be a relatively compact system, including a mobile housing (i.e. mobile by a single person) that is e.g. supported on wheels.
The afterloading device includes dedicated driven cables for moving the radiation source to one or more treatment locations. The afterloading device generally defines a plurality of channels from which a cable with a source can be fed into external tubes/catheters, connected to those channels. The known afterloader device includes a selector for selecting a channel that is to be used (i.e. that is to deliver a source to a respective catheter connected to the channel). The external catheters may be coupled to, provided with or include an applicator (or probe), known as such to the skilled person, the applicator being located at a desired treatment location (e.g. near or inside tissue that is to be irradiated). Alternatively, one or more external catheters may be used as such, as dose applicator(s).
In the present radiation delivery practice, the radiation dose to be delivered to the patient is calculated beforehand by a suitable dose planning system. For example, the dose planning system may be arranged to calculate the radiation dose around a suitable target volume for a configuration, when a sole radioactive source is to be positioned along a plurality of dose delivery channels (for example, catheters). In this case, the total dose delivered by such displaceable radioactive source will result from a convolution of the individual dose deliveries for each dwell position of the source inside the catheters.
The dose planning system is thus used for optimizing the number of the dwell positions of the radioactive source and the corresponding dwell times, so that the convoluted total delivered dosed corresponds to the dose shape and value, prescribed by the doctor/user.
The output of the dose planning system is a number of source dwell positions and dwell times. These data may be automatically loaded into the afterloading device for implementing the actual treatment.
Accordingly, it is of paramount importance that the actual position of the radioactive source corresponds to the prescribed position as calculated by the dose planning system. In order to verify the radiotherapy treatment in-vivo dosimetry is desired.
WO 2008/009917, incorporated by reference in its entirety in the present application, discloses a brachytherapy system, having an in-vivo dose detector, wherein the detector is insertable into and movable through a catheter, and comprises a sensor operable to detect radiation from a source used to irradiate a tissue to be treated in the course of an HDR brachytherapy treatment. The known dose detector comprises a diode sensor that is operable to generate an electronic signal which is fed to an electrometer or other voltage or charge measuring device external to the patient. In the known system the readings from the radiation detector are controlled by the timer which is switched on once it is assumed that the radiation source has reached its dwell position. Radiation emitted by the source in the dwell position is detected in real time and both the detector reading and the integrated dose for the treatment procedure may be logged in real time. The thus obtained radiation dose may be compared with the planned dose for that position and/or the integral dose. Should either of the parameters show a substantial discrepancy with the planned parameters, the treatment is aborted.
It is a disadvantage of the system of WO 2008/009917 that the installing of the radiation detector, requires feeding the detector into the one of the catheters and subsequently connecting the detector to an electrometer, which is cumbersome and takes-up a lot of time, therefore lengthening the overall patient treatment process. Further, the known system assumes that the radiation delivery source is accurately positioned at the prescribed dwell position. However, in practice minor or even substantial discrepancies may occur, for example either due to change in the treatment geometry (catheter displacement inside the patient), or due to an improper positioning of the source, leading to significant deviations in actual treatment doses.